Against the background of drastically rising global water demand and increasing pollution and overexploitation of regional water resources, the demand-driven water supply of households and industry is of central importance. Water reuse and desalination are seen as key technologies to overcome potential regional and local water shortage. In the joint projects funded by the German Federal Ministry of Education and Research (BMBF) ‘Future-oriented Technologies and Concepts to Increase Water Availability by Water Reuse and Desalination (WavE)’, evaluation approaches for analysing innovative technologies and concepts are being developed and assessed. All evaluation methods and criteria used were selected based on the decision situation at hand and the decision-makeŕs preferences. Based on the analysis of six multi-criteria evaluation concepts used in selected WavE projects, this paper presents a general approach for comparative multi-criteria evaluation of water reuse systems consisting of prerequisites, minimum requirements, evaluation criteria (qualitative, semi-quantitative or quantitative) and a final aggregation of results. Exemplary sets of criteria for the application in a more industrial, municipal and/or international context are presented as an aid for the application of holistic evaluation approaches for (process) concept and technology selection in the context of water reuse and desalination.

Treated wastewater is expected to constitute an essential part of the urban water cycle as an additional water resource in water-scarce or densely populated regions in the future. As decisions on the implementation of water recycling measures should always consider local conditions, the project ‘MULTI-ReUse: Modular treatment and monitoring for wastewater reuse’ has developed a comprehensive sustainability assessment tool, designed to support decision-makers in examining the technical feasibility, economic viability, ecological compatibility and social acceptance of alternative service water supply solutions at local level. This article describes the structure of this sustainability assessment tool and its underlying multi-criteria assessment approach based on 23 evaluation criteria. Already in the development phase, the tool was tested in a German and a Namibian case study. Both case studies are presented with a special focus on the technologies used and the results of the analysis with the sustainability assessment tool. Case study testing proved that the tool is applicable in various environmental and societal settings with widely differing climatic conditions, limited resource availability, for varying feed water qualities and water quality requirements. The comprehensive, straightforward assessment approach enabled the local users to identify the most sustainable supply system or strategy for their decision case.

Röntgenkontrastmittel, die in der medizinischen Diagnostik eingesetzt werden, werden über den Abwasserpfad entsorgt. Für Röntgenuntersuchungen kann der Einsatz von Kontrastmittel notwendig sein, die vom Körper binnen 24 Stunden mit dem Urin wieder ausgeschieden werden. Diese werden in Kläranlagen nur geringfügig entfernt und gelangen somit in den Wasserkreislauf. Da sie nur schwer biologisch abbaubar sind, reichern sie sich in unseren Gewässern zunehmend an, was Messergebnisse an der Ruhr belegen.

In vielen Ländern wird gereinigtes Abwasser aus Kläranlagen ohne weitere Verwendung in Vorfluter eingeleitet. Langfristig ist jedoch zu erwarten, dass gereinigtes Abwasser als zusätzliche Wasserressource in wasserarmen oder dicht besiedelten Regionen auch in Deutschland einen wesentlichen Bestandteil des urbanen Wasserkreislaufs darstellt.